Infected: Charger

CHARGER: Horrifically mutated, the Charger uses its oversized arm to its advantage, serving as an infected battering ram. The Charger is an effective class for scattering Survivors who play as a tight unit, separating them for attack.

In addition to knocking over Survivors, the Charger will also grab and carry them away from their teammates, where it will then smash them into the ground. -Left 4 Dead 2 Official Site

CHARGER: The Charger is a charging Special Infected that knocks down everything in his way. The Charger's main purpose is to separate a group of Survivors who are tightly joined by grabbing one and sending the other ones flying through the air (in the same way as getting punched by a Tank). While he matches the Survivors' pace, he speeds up considerably when charging them. However, this increase in speed leads to a slow stop and difficulty in turning. -The Left 4 Dead Wiki

CHARGER: The Charger, an infected with an enormously mutated right arm, can charge into the survivors, seize and separate one survivor from the others. -Wikipedia

A Charger in "Left 4 Dead".